Motor control circuit for regulating hydraulic pump of motor vehicle braking system, supplies back EMF to high-pass filter and square-wave signal to microprocessor for monitoring and signaling operating status

摘要

A high-pass filter (C4,R6) receives back EMF induced during switching off time in motor windings. A transistor (T2) produces a square-wave signal from the filtered high frequency signal and supplies the square-wave signal to a microprocessor for acquiring signal edges of high frequency components and signaling incorrect operating status if the number of signal edges does not exceed a predetermined threshold within specific time interval. The reduction in motor speed is recorded as an error status. The motor speed is controlled by pulse width modulation (PWM).